1. Field of the Invention
The present invention relates to programmable gate arrays and more particularly, to the use of software reconfigurable gate arrays to provide various measurement and stimulus functions for Automatic Test Equipment (ATE) systems.
2. Discussion of the Prior Art
Automatic test equipment (ATE) systems require various test instruments such as, a counter/timer, an arbitrary function generator and a digitizer, to provide the necessary measurement and stimulus functions for the test specifications of the units under test. In conventional ATE systems, each of the functions are provided in the form of stand alone test instruments which provide each individual function. The stand alone test equipment elements are tied together through a common bus but are housed in separate compartments. The system software for controlling the instruments is highly dedicated and modular. A central processor controls and communicates with each of the instruments through a central bus, typically an IEEE-488 bus. For each instrument, a corresponding software module exists to control its operation during test procedures. Examples of stand alone programmable test instruments that can be utilized in an ATE system may be found in U.S. Pat. No. 4,168,525 directed to a universal timer with selectable time base and clock output, U.S. Pat. No. 4,513,387 directed to a digital arbitrary function generator and U.S. Pat. No. 4,255,790 directed to a programmable pulse generating system.
These conventional test instruments require extensive logic circuits to perform the complex functions required for the instrument to operate and to be properly interfaced with the central processor. The design and hardware costs are high for each specialized circuit and a great deal of circuit board area is required, further increasing costs. Power consumption tends to be high, thereby generating excessive heat levels. Reliability is often not as high as would be desirable and trouble shooting is difficult and time consuming. In addition, redundant hardware is a problem as duplication wastes system space and generally causes a reduction in ATE system reliability and throughput as well as increasing maintenance costs.
In an alternative approach, suggested by Shivas in Automatic Testing 1979, functions common to each of the ATE test instruments would be provided in the form of modules that would be combined together under control of software to form the desired instrument. The Shivas proposal, called the "virtual instrument" contemplates a reconfigurable ATE system by interconnecting the basic building block modules required to perform the desired test functions. However, there is no disclosure of an actual implementation of the virtual instrument concept nor the necessary control interface between the processor containing the software and the instrument modules.